Tuna fisheries are a global industry focused on catching, processing, and trading tuna. This industry is a significant economic force, with the global market value reaching approximately $40 billion annually at the consumer level. Annual global catches of the principal market species often exceed five million metric tons. Managing this vast, lucrative, and globally distributed resource poses complex challenges for international governance and marine sustainability.
The Major Commercial Tuna Species
The commercial tuna industry primarily targets five species groups: Skipjack, Yellowfin, Bigeye, Albacore, and the three Bluefin species (Atlantic, Pacific, and Southern). These species differ significantly in their biology, market utilization, and the fishing pressure they face.
Skipjack accounts for the largest volume of the global catch, often making up more than half of the total. This species is generally the smallest and most abundant, primarily marketed as canned tuna products, resulting in a lower price per kilogram.
Yellowfin and Bigeye tuna are next in commercial importance. Yellowfin is popular for both canning and fresh fillets, while Bigeye is prized for the sashimi market due to its higher fat content.
The Bluefin species are the most valuable on a per-fish basis, generating billions due to their demand in high-end sushi and sashimi markets. Although their collective volume is less than 1% of the total global tuna catch, their high market price drives intense fishing pressure. Albacore is sought after for its white meat and is primarily used for premium canned tuna products, commanding a higher price than Skipjack.
Fishing Techniques and Associated Impact
Tuna are caught using various methods, each with a distinct environmental consequence, particularly regarding the accidental catch of non-target species, known as bycatch. Purse seining is the most common method, accounting for around two-thirds of the total global tuna catch, primarily Skipjack. This method involves encircling an entire school of fish with a large net, which is then drawn closed at the bottom.
A significant concern with purse seining is the use of Fish Aggregating Devices (FADs). These floating objects attract tuna but also cluster other marine life, leading to significant bycatch rates, sometimes reaching 15% to 20% of the total catch. Bycatch includes juvenile tuna, sharks, and rays.
Longlining uses thousands of baited hooks strung along miles of line, targeting larger, deeper-swimming tuna like Bluefin and Bigeye. This method often has the highest bycatch rates, sometimes exceeding 25% of the total catch. Longlining poses a risk to endangered species, including sea turtles, sharks, and seabirds, which are unintentionally hooked.
In contrast, the pole-and-line method and handline fishing are the most selective. They involve catching tuna one at a time with individual lines and barbless hooks. This selectivity virtually eliminates bycatch in most operations, achieving rates of less than 1%. It also allows for the immediate release of any undersized or non-target species.
Current Status of Global Tuna Stocks
Assessing the biological health of tuna populations is complicated by their highly migratory nature across vast ocean basins. Scientists differentiate between two statuses: “overfished,” meaning the population size (biomass) is too low, and “overfishing,” meaning the rate of fishing mortality is too high. A stock can be overfished while management measures allow the population to rebuild, or it can be a healthy size but experiencing unsustainable catch rates.
The majority of the 23 major commercial tuna stocks globally are currently at healthy levels of abundance, with approximately 65% meeting this benchmark. The resilience of Skipjack tuna stocks, which are generally well-managed, contributes to the overall positive outlook for global catch volume.
However, several stocks remain a concern, notably the Pacific Ocean bluefin, which is considered overfished despite a rebuilding plan being in place. Furthermore, some tropical stocks in the Indian Ocean, such as Bigeye and Yellowfin, are overfished and still experiencing overfishing due to insufficient management reforms. The constant movement of these species across international boundaries makes accurate stock assessment challenging, requiring consistent data collection and cooperation.
International Management and Conservation Efforts
The governance of highly migratory tuna resources is primarily conducted through five Regional Fisheries Management Organizations (RFMOs). These treaty-based bodies, such as the International Commission for the Conservation of Atlantic Tunas (ICCAT) and the Western and Central Pacific Fisheries Commission (WCPFC), are responsible for setting catch limits, monitoring stock health, and developing binding conservation measures for their respective ocean regions. RFMOs implement various strategies aimed at ensuring long-term sustainability. These measures include setting total allowable catch (TAC) limits, known as quotas, and establishing time and area closures to protect spawning grounds. Specific gear restrictions, such as rules governing the use of FADs, are also employed to reduce bycatch.
Beyond governmental regulation, consumer organizations and market-based programs promote traceability and sustainability. Certification programs, such as those run by the Marine Stewardship Council (MSC), evaluate fisheries against scientific standards for stock health and management effectiveness. This voluntary certification helps consumers identify tuna sourced from well-managed fisheries, creating market incentives for responsible practices.